Checking system for aircraft



July 8, 1941 H. R. HUGHES ETAL 2,248,351

mom@ SYSTEM Fon AIRCRAFT Filed June 14. 19'39 s sheets-sheet 1 l Cgil 74f/z 7a @e 95 4J 42 Y j( (Q /N VEN Tof@ 72 2755 g How/4 R0 A. HUG/456 /40,4,8/5 HA RR/J, lfm-CH, Fos TER a HARR/s /50 /53 7/ d 7o $5 Vl UAM July8, 1941. H. R. HUGHES ETAL.

CHECKING SYSTEM FOR AIRCRAFT Filed June 14, 193@ 5 Sheets-Sheet 2 July8, 1941- H. R. HUGHES ETAL. 2,248,351

cHEcxING SYSTEM FOR AIRCRAFT Filed June 14, 1939 s snets-sheex s wwf/vm@Hon/ARQ R. HUG/M5 STANLEY/J. BELL HAR/ams Mech/,Weens Patented July 8,1941 CHECKING SYSTEM FOR AIRCRAFT Howard R. Hughes, Houston, Tex., andStanley A. Bell, Glendale, Calif., asslgnors to Hughes Tool Company,Houston, Tex., a corporation of Delaware Application June 14, 1939,Serial No. 279,124

4 Claims.

Our invention relates to aircraft with special reference to aids foraircraft operators, and is directed to a system for checking thedisposition of important aircraft devices or members for given operatingsituations.

The numerous devices including instruments, auxiliary control members,and accessories on a modern aircraft make heavy demands on a pilot andoften tend to monopolize his attention at times when he should be freeto concentrate on maneuvering the ship. Even when his attention is notdiverted to observe or manipulate such devices, his mind mustcontinually revert to his responsibility for keeping the various devicesdisposed in accord with changing operating conditions. The seriousaspect of such dispersal of attention is that the harried pilot mayoverlook one or two adjustments or manipulations that are kof utmostimportance or absolutely essential for a given operating condition. Forexample.

of the numerous devices on an aircraft to be observed or adjusted priorto takeoff, two devices essential for safety might be retractable wingflaps for increasing lift and a valve controllable for temporarilydrawing upon an auxiliary supply of high-octane fuel. There is adistinct need for some means to reduce this burden on the pilot, atleast to the extent of warning the pilot when such requisitedispositions are not made to meet given operating situations.

The necessity for directing the pilots attention to imperativeadjustments of aircraft devices or members is pressing in makinglandings, especially emergency landings, and more especially if theparticular aircraft is an amphibian having retractable landing gears orretractable wing floats. At such a time the provision of some efficientmeans for rapidly checking the dispositions of paramount members anddevices preparatory for landing would permit the pilot to concentratewith unhampered mind on his task of appraising his flight problem,making sound decisions, and maneuvering his ship to the ground.

The general object of our invention is to meet the above expressed needfor some emoient and expeditious means for checking factors that arevital in a given operating situation. We propose lto reduce the checkingtask of the pilot to a simple checking movement or manipulation thatwill be immediately followed by some suitable warning signal if theselected devices or members of the aircraft are not properly disposedfor the operating situation confronting the pilot.

More specifically, it is our object to provide a checking system inwhich a signal means \is operatively related both to a manually movablechecking member and to one or more essential devices or members of theaircraft in such a manner that when the checking member is manipulatedto represent a given operating situation, a warning signal will followautomatically if said essential devices or members are not disposed asrequired by the given operating situation.

It is encumbent, of course. upon the pilot to manipulate the checkingmember to make the checking system effective whenever he is confrontedwith the given operating situation, and in some practices of ourinvention the pilot must train himself to turn to the checking system byhabit whenever the given operating situation arises. In one form of ourinvention, however, the checking system is operatively related to someaircraft means that is responsive to changing operating conditions or isresponsive to someI control movement or adjustment on the part o f thepilot that reflects or characterizes the given operating situation. Theimportant feature of such an arrangement oi our invention is that thesystem may thus be designed to function largely in an automatic mannerto warn the pilot to make the required checking manipulation wheneverthe given operating situation arises or is in prospect.

Another object of our invention is to provide a checking system of thecharacter described that is operable by a pilot and is combined with anindicating means responsive thereto for the attention of a co-pilot.

One important feature of our invention arises from the fact that thechecking system may be arranged to respond directly to the essentialmembers or devices to be checked whereby failure of such devices ormembers to respond to the pilots control means will be promptly revealedto the pilot. For example, failure of landing gear mechanism to functionwill not escape notice.

Further objects in mind are to make such a checking system serve morethan one operating situation when desirable, and to make such a systemrespond to as many devices or members of the aircraft as may beconsidered vital in each operating situation.

The above and other features and objects of our invention will beapparent from the detailed description to follow, taken with theaccompanying drawings.

In the drawings:

Fig. 1 is a side elevation partly in section of an apparatus that may beemployed in our checklng system;

Fig. 2 is a longitudinal section taken as indicated by the line 2-2 ofFig. 1;

Fig. 3 is an end elevation taken as indicated by the arrow 3 of Fig. 1;

Fig. 4 is a section taken as indicated by the line 4-4 of Fig. 1;

Fig. 5 is a section taken as indicated by the line 5-5 of Fig. 1;

Fig. 6 is a section taken as indicated by the line 5 8 of Fig. 1;

Fig. 7 is a view similar to Fig. 6 showing the mechanism in a secondposition;

Fig. 8 is a transverse section taken as indicated by the line 3-8 ofFig. 1;

Fig. 9 is a section through the casing of Fig. 6 taken as indicated bythe broken line 3-3 to reveal a portion of the mechanism in topelevation;

Fig. 10 is a diagrammatic representation of one form of our systemadapted to check the disposition of a single member or device of theaircraft;

Fig. l1 is a similar diagrammatic representation of our system asadapted to check a plurality of devices or members of an aircraft;

Fig. 12 is a diagram of a simplified form of our invention; and

Fig. 13 is a diagram of another form of our invention.

An understanding of our basic concept of a checking system may beapproached by first considering the diagrammatic representation in Fig.10. A switch arm normally having the neutrai position shown isoperatively connected with some indicating member to move therewith. Theswitch arm 20 is connected by a wire 2| with a grounded battery 22.Spaced to one side of the neutral position of the switch 20 is a contact23 connected by a wire 24 to a grounded lamp 25; and spaced from theswitch arm on the opposite side is a similar contact 2B connected by awire 21 to a second grounded lamp 23.

In its neutral position the switch arm 20 overlaps and touches twocontacts 23 and 30 that are connected respectively by wires 3| and 32 toswitches generally designated 33 and 34. The switches 33' and 34 areconnected in parallel through wires with a switch generally designated36, the switch 38 being in turn connected with a horn 31 or othersuitable signal means that is grounded, as shown, to complete thecircuit back to the battery 22. A red lamp 31a may be placed in parallelwith the horn 31 to be controlled simultaneously therewith, the red lampbeing visible to the pilot as a warning indicator to keep the pilot frombeing misled by failure of the horn. The switch 3B is operativelyconnected as indicated by the dotted line 38 with the throttle lever 38of the aircraft.

The purpose of the system shown in Fig. 10 is to check the dispositionof a retractable landing gear on an 4amphibian airplane. The twoswitches 33 and 34. therefore, are adapted to respond mechanically to amember L that is either one of the normal working parts of the landinggear mechanism or is operatively connected to such mechanism to be movedto a lower position when the landing gear is extended for land use andto an upper position when the landing gear is retracted for normalflight or' i'or landing on water. At the lower position the member Lpermits the switch 33 to close but holds the switch 34 open, and at itsupper position it permits the switch 34 to close but holds the switch 33open, both switches being con structed automatically to take closedpositions when not acted upon by the member L.

'I'he principle of operation may be readily understood from Fig. 10. Itis intended that the switch arm 20 will normally be in its neutralposition spaced from the contacts 23 and 26. but touching both thecontacts 29 and 30. Normally the circuit through the warning horn 31 andlamp 31a will be open because the switch 38 will normally be held openby the throttle 39. When the pilot prepares to make a landing, however,he will shift the throttle 39 to its 4 cut-off or idling position,thereby closing the switch 38, whereupon the warning horn 3l and lamp31a will be energized, since one of the two switches 33 and 34 will beclosed to complete the circuit through the switch arm 20. The warningsignal resulting from closing the circuit through the horn 3l and lamp21a will remind the pilot to check the disposition of the landing gear.He thereupon will swing the switch arm 20 downward if he is to land onground, or upward if he is to land on water. In the full line positionof the member L in Fig. 10 the member is holding the switch 34 open,thereby signifying that the landing gear is extended for landing onground. Swinging the lever 20 downward, then, to light the lamp 2l thatindicates "Land will cause the warning horn to be de-energized since theswitch arm in its downward posi-tion is spaced from the contact 29 andsince the contact 30 is cut oii' from the horn by the switch 34.

If the landing is to be made on water, the operator will swing the arm2li upward to energize the lamp 25 that indicates Water," but thewarning signal will continue without interruption because the switch 33is closed. To terminate the warning signals, the pilot must retract hislanding mechanism, whereupon the member L moving upwardly will open theswitch I3.

The situation of maneuvering to a landing is the given operatingsituation for which the system shown in Fig. 10 is designed, and it willbe readily apparent to those skilled in the art how such a checkingsystem may be adapted to cope with other operating situations. It is tobe noted that since the normal position of the throttle 33 for landingis the cut-ofi' or idling position, such position of the throttlecharacterizes the given operating situation and distinguishes thatoperating situation from at least most other operating situations. Bymaking the system responsive to movement of the throttle to thisthrottle position characterizing the given operating situation, we, ineffect, make our system responsive to the given operating situation andthereby provide for automatically warning the pilot when the systemshould be manipulated to check whatever devices are of utmost importancein the given operating situation. Instead of operatively relating thesystem to the cutout throttle, we may operatively relate the system toany means or mechanism on the aircraft that characterizes the givenoperating situation. Thus. for example. it will be readily apparent thatthe system may be responsive to a centrifugal switch that closes whenthe engine slows down, lust as the switch 36 closes to slow down theengine.

In the system constructed as above described,

failure of the warning signal means to -be energized when the throttleis closed down will mean that the switch arm 28 is displaced upward ordownward from its normal neutral position. One of these positionsprecluding a horn signal might, however, represent the wrong dispositionof the landing gear. For example, if the switch arm 28 were in its lowerposition when the operator closes down the throttle to land on water,the horn 31 would not be energized to warn the pilot. It is true that insuch a situation the lamp 28 designating Land would be energized and tothat extent serve warning that'the landing gear is not properly disposedfor landing on water. We prefer, however, not to depend solely on one ofthe indicating lamps in such a situation and for this reason, amongothers, we prefer to incorporate in such a system delayed action meansto return the switch arm 28 automatically to its neutral positionwhenever it is shifted in either direction from that position, thereturn movement being completed in a desirably extended time interval.By virtue of this provision, we insure the switch arm 28 being in theneutral position whenever a landing is to be made and,

incidentally, we avoid unnecessarily prolonged energization of eitherlamp 25 or lamp 28.

The embodiment of such a system in a suitable physical structure iswithin the skill of those conversant with the art. At least no furtherdescription is necessary of the two switches 33 and 84, the switch 38,the warning horn 81, and the lamp 31a. The following detaileddescription, however, will be helpful in suggesting how the electricalelements associated with the switch -arm 28 and the delayed-action meansfor moving the switch arm may be provided in a compact arrangement at ornear the instrument board of an aircraft.

Preferably the manually operable switch arm 28, the associated contacts,the lamps 25 and 28, and the delayed-action means for operating saidswitch arm are all housed in a casing that fronts on the instrumentboard of the aircraft. Such a casing 48 as shownin Figs. 1 and 2 maycomprise a cylindrical shell 4| removably mounted on a head member 42and secured thereon by suitable screws 43.

The shell 4| has an end wall 44, to the inner face of which a bracket 45of insulating material is mounted by suitable screws 48. The bracket 45carries three inwardly directed electrcal plugs 41, 48, and 48 connectedrespectively to wires 2|, 3|, and 32, each of the plugs having a nut 58to engage the corresponding wire. erably the end wall 44 is aperturedand provided with a suitable bushing 5| through which the wires arepassed from the exterior of the casing. The head member 42 is preferablyin the form of a cylindrical casting having a radial flange 53 tofacilitate mounting the casing on the instrument board.

The head member casting 42 forms a light chamber 54 containing the lamp28 and a second light chamber 58 housing the second lamp 28, the twochamber being separated by a partition 5 8. The light chambers 54 and 58have openings in the face of the head member, which openings may becovered by windows 88 and 8| respectively. Preferably the window 88 hasetched or otherwise marked thereon the word Water and the window 8| issimilarly marked with the word Land Since a manually operable checkingmember in the form of a lever 88 is mounted on the face of the headmember to swing toward Preff either of the two windows 88 and 8|, theface may be marked with an arcuate line 84 with arrow-shaped ends toindicate the directions of such movement from an intermediate neutralposition. v

'I'he head member 42 is bored and tapped to receive the threaded ends ofthree rods 85 by means of which the mechanism within the casing 48 issupported from the head member. The three rods 85 engage the followingmembers in the following order: spacer sleeves 88 adjacent the headmember 42; a laminated switch block 88; a casing plate 18; spacersleeves 1| abutting the casing plate 18; a secondl casing plate 12abutting the ends of the spacer sleeves 1|; a third set of spacersleeves 13; a plate 14 abutting the spacer sleeves 18; and, finally,nuts 15 to hold the foregoing assembly together. The casing compartment11 in the casing 48 defined by the casing plate 18 and the head member42 is a switch compartment. The casing compartment 18 defined by thecasing plates 18 and 12 houses the means for returning the switch arm 28to neutral position. The clockworks for regulating the rate at which theswitch arm 28 is returned to the neutral position is installed in thecasing compartment 18 between the casing plates 12 and 14.

The checking lever 83 is secured by a pin 88 to the protruding end of ashaft 8| that extends through a suitable bore 82 in the partition 58 ofthe head member 42, the shaft being further journaled in bearings 88 and84 in plates 18 and 12 respectively and being formed at its inner endwith an annular flange 85 in abutment with the bearing 84 to preventaxial movement outwardly. The primary purpose of the shaft 8| is tocontrol the switch arm 28 in the casing compartment 11.

The switch arm 28 secured on the shaft 8| by a pin 88 comprises a block88 of insulating material and a pair of spaced parallel switch blades 8land 82. Each of the switch blades is apertured to receive a pair ofscrews 83 by which they are attached to the block 88, a small plate J 84of conducting material serving as a spacer between the two blades. Thelaminated switch block 88 with which the switch arm 28 cooperatesincludes two U-shaped insulating plates 85 and 88 of a configurationbest shown in Fig. 5 and an intermediate U-shaped insulating plate 81.The intermediate plate 81 is separated from the two adjacent plates 85and 88 of the switch block assembly by spacer sheets 88 of insulat-r ingmaterial and is lesser in radial dimensions than the plates 85 and 88 toprovide an arcuate recess 88 into which the two switch blades 8| and 82extend. Within the arcuate recess 88 on the inner face of the insulatingplate 85 are mounted the two previously mentioned contacts 23 and 28 inthe form of strips of metal, the contacts being so positioned that theswitch blade 8| lies against the contact 23 when the checking lever 83is moved toward the window 88 marked Water" and lies against the contact28 when the checking lever is shifted toward the window 6| marked LandThe contact 23 has a anged portion |88 extending through an aperture |83in the insulating plate 85 (Fig. 5) and the contact 28 has a similaranged portion |84 extending through a second aperture |85 in theinsulating plate 85, these two flanged portions being connected by thewires 24 and 21 respectively to the two corresponding lamps 25 and 28 inthe light chambers.

Also within the arcuate recess 99 are the two previously mentionedcontacts 29 and 30 mounted on the inner face of the insulating plate 96for cooperation with the switch blade 92. These two contacts haveflanged portions (not shown) similar to the flanged portions and |04extending through apertures (not shown) in the insulating plate 96whereby the contacts 29 and 30 may be connected in the requiredcircuits.

The circuits associated with the switch arm are established through thepreviously mentioned plugs 41, 48, and 49. For this purpose we mount onthe face of the plate 14 a bracket ||0 carrying three jacks II, ||2, andH3 positioned to receive plugs 41, 48, and 49 respectively. The jack isconnected to a wire ||6 (Fig. 5) that terminates at one of the screws 93and is thereby electrically connected with the two switch blades 9| and92. The jacks ||2 and ||8 are connected respectively with the contacts28 and 30.

The actuating means for returning the switch arm 20 toits normal neutralposition touching both contacts 29 and 30, and for simultaneouslyreturning the checking lever 63 to its corresponding neutral positionincludes a plate assembly generally designated H8, comprising two plates|20 and |2| in the casing compartment 18. The two plates are connectedtogether by a pair of screws |22 through a spacer block |23 (Fig. 7), bya stud |24 having threaded ends engaged by nuts |25, by a screw |26, andby a screw |28 extending-through a spacer sleeve |29. 'I'he plateassembly H5 is mounted on a pair of links |30 and a second pair of links|3I. Each of the links |30 is apertured at one end for rotatablemounting on the shaft 8| and is apertured at the other end to pivotallyembrace the spacer sleeve |29 on the screw |28. The second pair of links|3| swings from a ratchet shaft that extends through slots |36 and |31in the plates |20 and |2| respectively, the two links being between theplates and on opposite sides of a ratchet wheel |38 that is keyed to theratchet shaft |35. It is apparent that by virtue of the two pairs oflinks the plate assembly will be free to reciprocate and will be guidedby the two pairs of links, the range of reciprocation being determinedby the slots |36 and |31.

Movement of the plate assembly ||9 in one direction of its range ofreciprocation is accomplished through a rocker |40 that is secured tothe shaft 8| by a pin |4|, the rocker being mounted between the twolinks |30. One arm |42 of the rocker |40 carries a roller |43 positionedto press against a face of the spacer block |23 and the other arm |44 ofthe rocker is positioned to move against the spacer |29 on the screw |28of the rocker assembly, the end of the arm |44 being recessed to conformwith the periphery of the spacer 28. By virtue of this arrangementrotation of the shaft 8| in one direction will cause the arm |42 to movethe plate assembly I9 away from the shaft, and rotation of the shaft 8|in the opposite direction will cause the arm |44 to move the plateassembly away from the shaft in the same manner.

To return the plate assembly toward the shaft 8| thereby to return themaster lever 63 to its neutral position, we provide in the preferredform of our invention two helical springs |45, one on each side of theplate assembly. ne end of veach of the springs |45 may conveniently beconnected to the corresponding nut I 25 on the end of the stud |24. Foranchoring the opposite ends of the two springs |45 we prefer to employmeans that includes a relatively large pin |41 (Figs. 2 and '7)extending through the two casing plates 10 and 12, the pin being heldagainst axial movement by a head |48 formed in one end and by a cotterkey |49 extending through the other, and mounted on the pin |41 betweenthe two casing lplates 10 and 12 is a pair of arms |50 held in spacedrelation by three spacer sleeves |5I. Fixedly attached to each of thesearms |50 is a nut |52 which receives the end of a suitable screw |53extending from the adjacent casing plate 10 or 12. The two springs |45are anchored to the nuts |52, the described arrangement serving to holdthe nuts rigidly in position against the force of the springs.

To retard the spring-actuated movement of the plate assembly ||9, wemount a pawl |55 on the screw |26 that both interconnects the links |3|and connects the links with the plate assembly. The two links |3| extendbeyond the screw |26 and are interconnected at their outer ends by apair of screws |56 extending through a spacer block |51. On this spacerblock is mounted a suitable leaf-spring |58 that continuously urges thepawl |55 toward the periphery of the ratchet wheel |38 whereby the pawlmay engage one of the teeth |59 of the ratchet wheel. Whenever rotationof the master lever 63 shifts the plate assembly ||9 to the limitpermitted by the slots |36 and |31 of the plate assembly the pawl |55engages one of the ratchet teeth |58 whereby the spring-actuated returnmovement of the plate assembly necessarily rotates the ratchet wheel.Whatever retards movement of the ratchet wheel will correspondinglyretard movement of the master lever 63 and the corresponding movement ofthe switch arm 20.

In the preferred form of our invention shown in the drawings the meansfor retarding the movement of the ratchet wheel |38 is the clockmechanism in the casing compartment 19, the clock mechanism being drivenby the two springs |45 through the medium of the ratchet wheel. Theratchet wheel |38 is keyed to the ratchet shaft |35 and the ratchetshaft is rotatably mounted in bearings and |6| in the two casing plates10 and 12 respectively. The ratchet shaft |35 extends into the casingcompartment 19 and has an axial bore in its end to receive the shaft |64on which the rst gear |65 of the clockworks is mounted, a setscrew |66in the ratchet shaft extending into the bore into engagement with thegear shaft |64.

The clockworks is carried by the plate 14 and a spaced parallel plate|68 connected thereto by four studs |69. In the particular constructionshown, the first gear of the clock mechanism engages a pinion |1| on ashaft |12 that carries a second gear |13. The second gear in turnthrough a pinion |14 on a shaft |15 drives a third gear |16. Finally,the third gear engages a pinion |11 (Fig. 1) on a shaft |18 to which iskeyed an escapement wheel |19. Rotation of the escapement wheel iscontrolled in the well known manner by a forked lever and cooperatingbalance wheel |8| (Fig. 8).

Since the mechanism shown in Figs. 1 to 9 is a part of the previouslyexplained system shown dlagrammatically in Fig. 10, the operationthereof will be obvious from the above description. Normally thechecking lever 63 will be in the neutral position shown in Fig. 3, theassociated switch arm 20 being likewise in its neutral position. Whenthe pilot throttles down for a landing, he will flip the checking leverupward or downward according to whether he is to land v movement of thechecking lever to be' delayed a matter of, say, two minutes, and theplane has not alighted within that time the warning horn and red lampwill again be energized but may be readily stopped by the operator againflipping l `the checking lever towards the. required checkt ingposition.

In Fig. 11 lwe show diagrammatically how our t' system may be designedto respond to more than one deviceor-memberl of the aircraft. -Iiorex-f.

ample, X and Y may represent two membersvor wire 220 to a switch 22|that is in turn connected to the switch I!! by a wire 222. Whenever thelanding gear of the airplane is properly extended for a landing, themember G is in an upper position indicated in dotted lines at whichupper position it holds open the switch 22 I. l

` In a system such as shown in Fig. i2, it is not necessary'to have anindicator lamp energized to show the position of the switch arm |20, noris it necessary to provide any delayed action means for moving theswitch arm to either of its two positions. Whenever the pilot throttlesdown his motor, he thereby closes the switch |22. If

the switch arm |22 is touching the contact |22 when the switch |25 isclosed by the throttle, the alarm signalv means will be energized towarn the pilot to shift the switch arm |22 to its upper or checkingposition whereupon the alarm signal A y will continueto be energizedunless or until the devices of the aircraft which should be in their ysented by the lamp 25a and should be in their llanding gear is extendedto cause the switch 22| ment, the absence ofthe signal will indicatethat lower positions for an operating situation represented by the lamp22a. The system shown in Fig. 1i is for themost partv identicalv withthesystem shown'in Fig. l0, correspondingnumerals with the sumx "a" beingemployed `to designate corresponding parts.v It will be noted that themember X is operatively relatedl to the twoswitches 22a and 24a inthe'same manner as the member L of Fig. is related to the correspondingswitches 22 and 22. A switch |22 iselectrically 'connected in parallelwith the switch I 22a by a wire |88 and a similar switch |21 is placedin parallell with the switch 22a by a wire |22, and the member Y isyadaptedyto open the switch |25 in its upper vposition and to open theswitch |21 in its lower position. If the switch' l arm 22a in Fig. 11 ismoved upward to energize i the indicator lamp 25a. the `warning signalmeans will be energized unless or until both of the members X andl Y arein their upper positions tocut of! both the switches 22a and |85.

In like manner, both the members X andY must be in their lower positionsto cut oi! the-warngized by the switch arm a. a

Fig. 12 `shows diagrammatically how our invention in simpliiled formvmaybe applied to the sole problem of insuring that a retractable land-l inggear of an aircraft be properly extended.

whenever the pilot reduces the power to glide to a landing. The switcharm .|22 either constitutlines at which it touches a contact |82a andthe dotted line position at whichv it touches a ing signals when theindicator lamp 22a is ener.v

contact |22, the switch arm being adapted in any suitable manner toavoid maintaining any intermediate position out of touch with 'either ofthe two contacts.v The contact |82 is connected by a wire |24 to oneside oi' a switch |25, the other side of the switch |25 being connectedby a wire |92 to a grounded electrical horn |21. Here again a red lamp|21a may be placed in parallel with the horn |21 as an auxiliary warningmeans. The switch |25 is operatively connected to the throttle |22through a suitable mechanical connection indicated by the dotted line|22 so` that the switch |25 closes when the throttle |92 is movedtowards its cut-oi! position. The contact |22 is electrically connectedbya 'the switch arm |22 is already in checking position and that thelanding gear is extended. Buch would be the condition of the system ifthe pilot had neglected to retract his landing gear after taking oil. ,hl l In the form of our invention indicated diagrammatically in Fig. 13,the same structure is employed as heretofore-described with reference toFigs. 1 to 8. The elements of the diagram in Fig. 13 that are containedin the mechanism casing 4I on the instrument board of the aircraft arevidentical with corresponding elements of Fig. l0, correspondingnumerals with the suiiix b being employed to designate correspondingparts.` It will be noted that the switch arm 2lb cooperating with thecontacts 22h, 22h'. 2lb, and 22h controls circuits through the two wires2lby and 22b leading from the casing, and also 'oontrcls energization ofthe lamp 2lb referring to landing onwater and the lamp 22h referring tolanding on land. The switch arm 2lb in Fig. 13 is notdirectly connectedwith a battery 2|l for energizing the system, but is in electricalcommunication with the battery through a grounded wire 2|| attached tothe switch arm and a second grounded wire 2|2 connected with one pole ofthe battery.

The wire 2lb leads to a switch member 2M movable between an upperposition touching a contact 2li and a lower position touching a contact2H, the switch arm being adapted to have a tendency when unopposed tomove against the lower contact 2li. In like manner the wire 22h leads toa second switch member 2|1 that is movable between an upper contact 2|!and a lower contact 2|2, the switch member having an inherent tendencyto move against the upper contact 2|2. The two contacts 2li and 2|2 areinterconnected by a wire 222 and both are connected to one side of agreen lamp 22| by a wire 222, the other side of the lamp being connectedto the battery 2||I by a wire 222. The two contacts 2|2 and 2| 2 areinterconnected by a wire 225 and by the same wire are connected to asecond wire 228. The wire 222 is connected to one terminal of a red lamp221 and has a branch wire 222 leading to a switch arm 222 that ismechanically connected to the throttle lever 22| of the aircraft throughmechanical means indicated by the dotted line 222. 'I'he switch arm 220cooperates with a contact 222 that is connected by a wire 224 with oneterminal of an electric horn 23|. From the battery 2|il a wire 228branches to connect with the second terminal of the red lamp 221 andwith the second terminal of the horn 22S.

The member L of Fig. 13, as previously mentioned with reference to Fig.10, is operatively associated with the landing gear mechanism of theaircraft and is movable between an upper and a lower position inaccordance with retraction or extension of the landing gear. In theupper position of the member L shown in full lines in Fig. 13 the switchmember 2M is forced against the-contact 2li, but the lower switch member2|1 is free to iollow its inherent tendency to abut the contact 2li. Inthe lower position of the member L indicated by dotted lines in Fig. 13,the upper switch member 2H is free to swing against the contact 2li. butthe lower switch member 2|1 is at such time forced away from the contact2i! and against the contact 2H.

Fig. 13 shows the disposition of the switch arm h Just after it has beeniiipped upward by the pilot for a checking operation preliminary to alanding on water. 'Ihe lamp 2lb is energized through the contact 22h toilluminate the word "Water" on the instrument panel and the switch armalso touches the contact 2lb to connect the wire IIb to ground. 'I'helanding gear of the aircraft being properly retracted for alighting onwater, the member L is holding the switch member 2M against the contact2li thereby completing a circuit for energizing the green lamp 22|. Thelower switch member 2i1 is against the contact 2|. but neither the redlamp 221 nor the warning horn 22| is energized since the switch arm 2lbis spaced from the contact 2lb. It is apparent that the energization ofthe green light 22| indicates that the landing gear is in properdisposition for the operating situation that is represented by theenergization of the lamp 2lb; Ii the landing gear were not properlydisposed for the maneuver in prospect as represented by energization ofthe lamp 25h, the switch member 2M would lie against the contact 2| 0 tocomplete a circuit for energizing the red lamp 221 and the warning horn235. Since the red lamp 221 has a direct connection with the battery 2Ilit would be energized whenever both the switch arm 20h lies against thecontact 2lb and simultaneously the switch member 2M lies against thecontact 2| 6, but energization of the warning horn 22B requires inaddition the closing of the switch 230 in response to movement of thethrottle 22| in the direction to reduce power. Il the landing gear isnot properly disposed for alighting on water, the lamp 221 willtherefore give advanced warning from the moment the switch arm 2Gb isflipped upward, and i1' the disposition of the landing gear is notchanged the warning horn 2li will subsequently come into operation whenthe pilot attempts to glide with reduced power.

For a checking operation prior to making a landing on ground, the pilotwill shift the switch arm 20h to its lower position to energize the lamp28h that illuminates the word Land" on the instrument board. If thelanding gear in such a situation is properly extended, the switch member2|1 will be held against the contact member 2|! by the member L tocomplete a circuit through the green lamp 22|. but the fact that theswitch member 2li will at the same time lie against the contact 2|! willnot such case the pilot may cause energization of either the red lamp221 or the horn 22B because the switch arm 2lb is spaced from thecontact 23h. On the other hand, ir the member L is not in the positionrequired for the operating situation that is represented by energizationof the lamp 2lb, the switch member 2H will lie against the contact 2liwithout energizing the green lamp 22|, but the switch member 2|1 willlie against the contact 2|! to energize the red lamp 221 andsubsequently to energize the warning horn 22! upon leftward movement o1'the throttle 22|.

Whether the aircraft is lo be set down on land or water, movement of thechecking member that controls the switch arm 20h will cause energizetionof the green lamp 22| if the landing gear is in the proper disposition.It may be noted, however, that if the intended maneuver is not completedwithin the interval of operation provided by the clockworks thatregulates the return movement of the switch arm 20h, the switch arm 2lbwill in the course of the maneuver reach its neutral position to touchthe contact 2lb whereupon both the green and red lamps will be energizedsimultaneously andthe horn will also be energized if the aircraft powerplant is throttled down. In cut oil' the red iight and the horn merelyby again shifting the checking member in the direction corresponding tothe maneuver that is being performed.

In the course of normal flight, both the red lamp and the green lampwill be energized because the normal position of the switch arm 2Ib isat neutral touching both of the contacts 2lb and 2lb. As far as theinstrument board is concerned, then, the purpose oi' the pilot inmanipulating the checking member that controls the switch arm 2lb is toput out the red light 221, leaving only the green light 22| energized.To put out the red light, he must manipulate the checking member toenergize either the lamp 2lb or the lamp 2lb according to whether heintends to alight on water or land. Should the pilot neglect to employthe checking system oi' Pig. 13, he will be reminded of that fact assoon as he shuts oi! power to glide, since leltward movement of thethrottle 22| will close the-circuit through the checking member to checkthat disposition.

Since it may be desirable in some installations to have the checkingsystem oi' Fig. 13 under the observation of a co-pilot or other memberot the crew at a second station on the ship, we show in Fig. 13 a lamp221 in parallel with the lamp 2lb, a lamp 222 in parallel with the lamp2lb, a lamp 238 in parallel with the lamp 22|, and a lamp 24| inparallel with the lamp 221, these four auxiliary lamps being located atthe second station on the aircraft, the first two lamps being suitablydesignated "Water and "Land" respectively, and the The diagrams andspeciilc embodiments chosen for the purpose of disclosure and toillustrate the principles involved will suggest to those skilled in theart various changes, modincations, and subception. We specificallyreserve the right to all such changes, modifications. and departuresthat properly come within the scope of our appended claims.

We claim as our invention:

1. In an aircraft, means to check the disposition of an aircraft memberthat is movable into second checking position; a second indicator cirandout of a given position for a given operating situation, said checkingmeans including: a checking member movable between a first positionnormal for flight and a second positionI said second positionrepresenting said operating situation for the purpose of checking thedisposition of said aircraft member; means on the aircraft adapted totake a position characterizing said given operating situation when saidoperating situation arises; means responsive to said checking member andsaid aircraft means to give a signal when said checking member is insaid rst position and said aircraft means is in said characteristicposition, said signal being a reminder that said checking member shouldbe moved to said second position for checking the disposition of saidaircraft member for said operating situation: and means responsivetosaid aircraft mem.- ber, to said checking member, and to said aircraftmeans to give a warning signal when said aircraft member is 'out of saidgiven position while said checking member is in said second position andwhile said aircraft means is in said characteristic position.

` tion of an aircraft member that is movable between a first positionrequired for a first operating situation and a second position requiredfor a second operating situation, said checking means including: achecking member adapted to be moved by the aircraft operator from aneutral position either to a first checking position repre senting saidfirst operating. situation or to a second checking position,representing said second operating situation; a first indicator circuitrepresenting said first operating situation; a switch in said circuitresponsive to said aircraft member to open when said aircraft member isin its first position and to close when said aircraft member is in itssecond position; a second switch in said circuit operatively connectedwith said checking member, said second switch being adapted to closewhen said checking member isin either said neutral position or saidfirst checking position and to open when said checking member is in saidcuit representing said second operating situation: a switch in saidsecond circuit responsive to said aircraft member to open when saidaircraft member is in its second position and to close when saidaircraft member is in its first position; a second switch in said secondcircuit operatively connected with said checking member. said secondswitch in said second circuit being adapted to close when said checkingmember is at either said neutral position or said second checkingposition and to open when said checking member is at said first checkingposition; a third switehin each of said two circuits in series with theother recited switches of said circuits, said third switch beingresponsive to a flight-control member of the aircraft and being adaptedto close whenever said flight-control member is moved to a positioncharacterizing both said operating situations; and signal meansresponsive to closing of either of said circuits whereby a remindings181111 will be given whenever said flight-control member is i moved to,said characteristic position while said checking member is in saidneutral position and whereby a warning signal will be given wheneversaid flight-control member is at said characterizing position andsimultaneously said checking member is at one of said checking positionsand said aircraft member is out of the position corresponding to theoperating situation represented by the position of saidl checkingmember.

3. A checking means as setforth in claim 1 that includes delayed-actionmeans to move said checking member automatically from said secondposition to said normal first position.

4. A checking means as set forth in claim 1 that includes an additionalsignal means responsive to said checking member to indicate when thechecking member is in at least one of its two positions whereby aco-pilot may be' informed of changes in the disposition of the checkingkmember made by the pilot.

' Howsan a miams.

sumar a. nicht..y

